<p>Among reactive oxygen species, singlet oxygen (¹O₂) is the preferred agent for photooxygenation reactions owing to its exceptional reactivity and selectivity. However, the coexistence of reactive oxygen species such as O₂^<b>·</b>⁻, ^<b>·</b>OH and ¹O₂ is a long-standing challenge in photocatalytic systems, as it leads to undesired deactivation pathways (for example, Haber–Weiss reactions) and reduced selectivity. Here we design a thiophene-anthraquinone photocatalyst, named AQ-S, which generates ¹O₂ through an ultrafast Dexter-type cascade process originating from a superoxide-like exciplex, as confirmed by both experimental results and complete active space self-consistent field calculations. AQ-S effectively promotes the photogeneration of ¹O₂ over superoxide radicals, resulting in ultrafast H₂O₂ photogeneration (11.4 mmol g⁻¹ h⁻¹ in batch reactions and 72.6 μmol h⁻¹ in flow reactions using only H₂O and O₂). The radical-free cascade process enables unique pathways in oxidation reactions (such as, N–N coupling for azo derivatives and alkene cleavage), distinct from systems relying on electron transfer-mediated radical pathways. Our study provides a mechanistic framework for exciplex-mediated ¹O₂ generation and demonstrates its potential in photocatalysis.</p><p></p>